Is that really so surprising? It really doesn't even take a nation state if the people are talented enough and keep a low profile. As he said, they could be from anywhere. Could be the NSA doing it to force companies to keep innovating defenses. As long as the two parties keep evolving technologically faster than everyone else and don't push things too far that they break the internet, they're keeping the internet running and getting stronger. By doing it at a measured pace, the attacker is broadcasting the rate of evolution required by industry to keep the internet safe.

On the other hand, DDoS attacks provide a great cover for other more targetted attacks. For instance, probe for vulnerabilities that might be exposed by shortcuts taken to guard against the DDoS attack and use those to worm you way inside.